Improve equipment texture performance and accuracy

Cache composite textures by input key so identical NPC equipment
combos share one GPU texture. Use DBC layout system for
ItemDisplayInfo texture component fields instead of hardcoded
indices (cross-expansion support). Selective player equipment
re-emission on item query response instead of broadcasting to
all players.

src/rendering/character_renderer.cpp

@@ -572,6 +572,21 @@ GLuint CharacterRenderer::compositeTextures(const std::vector<std::string>& laye
 GLuint CharacterRenderer::compositeWithRegions(const std::string& basePath,
                                                 const std::vector<std::string>& baseLayers,
                                                 const std::vector<std::pair<int, std::string>>& regionLayers) {
+    // Build cache key from all inputs to avoid redundant compositing
+    std::string cacheKey = basePath;
+    for (const auto& bl : baseLayers) { cacheKey += '|'; cacheKey += bl; }
+    cacheKey += '#';
+    for (const auto& rl : regionLayers) {
+        cacheKey += std::to_string(rl.first);
+        cacheKey += ':';
+        cacheKey += rl.second;
+        cacheKey += ',';
+    }
+    auto cacheIt = compositeCache_.find(cacheKey);
+    if (cacheIt != compositeCache_.end() && cacheIt->second != 0) {
+        return cacheIt->second;
+    }
+
     // Region index → pixel coordinates on the 512x512 atlas
     static const int regionCoords[][2] = {
         {   0,   0 },  // 0 = ArmUpper
@@ -717,6 +732,7 @@ GLuint CharacterRenderer::compositeWithRegions(const std::string& basePath,
 
     core::Logger::getInstance().info("compositeWithRegions: created ", width, "x", height,
         " texture with ", regionLayers.size(), " equipment regions");
+    compositeCache_[cacheKey] = texId;
     return texId;
 }